If you jump and touch the wall behind behind them while they are in the corner you lose the b,f charge as it thinks you are crossing them up but then land in front of them. As you can still do j.MK, cr.MP xx flash kick.
Explanation:
If you go into training mode and turn the hit boxes on you see a red dot at your feet signifying the centre of you character.
Now when you jump over a fully cornered opponent and touch the wall above their head your red dot just goes over their red dot there fore the game thinks you have gone over them and lose your charge but then you land in front instead.
I’m pretty sure this happened in classic ST as well. I remember doing a lot of jump straight up roundhouses to start combos against cornered foes (using Claw).